Geometry began as the art of measuring the shape of land so that it could be shared fairly between people. The word "geometry" means "to measure the land". It has grown from this to become one of the most important parts of mathematics. The GreekmathematicianEuclid wrote the first book about geometry. Geometry is one of the oldest branches of mathematics.

A straightline is the shortestdistance between two points. For example, Sophie pulls a piece of string from one point to another point. A straight line between the two points will follow the path of the tight string.

A plane is a flat surface that does not stop in any direction. For example imagine a wall that extends in all directions infinitely.